Globalization challenges the existence of a mimetic relationship between citizenship and the nation-state. Homogeneous identities, based on ideological notions such as «national language», are problematic in societies where linguistic and identitarian diversity has grown considerably. Catalonia is a territory in which a portion of the population claims a Catalan identity that differs from the Spanish identity and vice versa. A common theoretical assumption is that the Catalan identity coexists with the Catalan language. Therefore, some people defend the presence of Catalan at school as a source of national identity, while others defend its use as a way to learn a second language that cannot be learnt within the family or the social context. In the last few years Catalonia has received nearly one million immigrants and the sociolinguistic situation has become more complex. The latest available survey shows that 6.3% of the population in Catalonia mainly uses a language other than Catalan or Spanish. Within this context, the authors trace the identity construction of a group of teenagers approximately fifteen years of age and of immigrant origin. Data were collected through two focus groups of six to seven students with different backgrounds, languages and length of residence in Catalonia. The results underscore the importance of origin in identity construction. In addition, according to the results, the participants who felt Spanish or Catalan related such feelings not with the language, but with their social exchanges with native peers. Participants’ comments also showed the difficulties involved in promoting multiple identities at school to prevent racist and xenophobic attitudes and to promote future collaborative projects where people can live together with their differences